package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.RedisData;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;
import java.security.Key;
import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.*;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Resource
    private StringRedisTemplate stringRedisTemplate;

    /**
     * 根据id查询商铺信息
     * @param id 商铺id
     * @return 商铺详情数据
     */
    @Override
    public Result queryById(Long id) {
        // 缓存穿透
        //Shop shop = queryWithPassThrough(id);

        //互斥锁解决缓存击穿
        //Shop shop = queryWithMutex(id);

        //逻辑过期解决缓存击穿
        Shop shop = queryWithLogicalExpire(id);
        if (shop == null){
            return Result.fail("店铺不存在:");
        }

        //返回

        return Result.ok(shop);
    }


    private static final ExecutorService CACHE_REBUILD_EXKECUTOR = Executors.newFixedThreadPool(  10);

    public Shop queryWithLogicalExpire(Long id) {
        String key = CACHE_SHOP_KEY + id;

        //1. 从redis查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isBlank(shopJson)){
            //3. 存在，直接返回
            return null;
        }
        //4.命中，需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        Shop shop = JSONUtil.toBean((JSONObject) redisData.getData(), Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())){
        //5.1 未过期，直接返回店铺信息
            return shop;

        }
        //5.2 已过期，需要缓存重建

        //6.缓存重建
        //6.1 获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        //6.2 判断是否获取成功
        boolean isLock = tryLock(lockKey);
        //6.4 获取锁成功，开启独立线程，实现缓存重建
        if (isLock){

            CACHE_REBUILD_EXKECUTOR.submit(() -> {
                try{
                //重建缓存
                this.saveShop2Redis(id, 20L);
            }catch(Exception e){
                throw new RuntimeException(e);
            }finally{
                    //释放锁
                    unLock(lockKey);
            }


            });

        }
        //7.返回
        return shop;
    }




    public Shop queryWithMutex(Long id) {
        String key = CACHE_SHOP_KEY + id;

        //1. 从redis查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isNotBlank(shopJson)){
            //3. 存在，直接返回
            return JSONUtil.toBean(shopJson, Shop.class);
        }
        //判断命中是否为空值
        if (shopJson != null){
            return null;
        }
        //4.实现缓存重建
        //4.1 获取互斥锁
        String lockKey = "lock:shop" + id;
        Shop shop = null;
        try {
            boolean isLock = tryLock(lockKey);
            //4.2 判断是否获取成功
            if (!isLock){
                //4.3 失败休眠重试
                Thread.sleep(50);
                return queryWithMutex(id);
            }
            //4.4 成功，返回
            shop = getById(id);
            //模拟重建的延迟
            Thread.sleep(200);
            //4.不存在，根据id查询数据库

            //5.数据库不存在，返回错误
            if (shop == null){
                //将空值写入redis
                stringRedisTemplate.opsForValue().set(key, "",CACHE_NULL_TTL, TimeUnit.MINUTES);
                // 返回错误
                return null;
            }
            //6.存在，写入redis
            stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }finally {
            //7.释放互斥锁
            unLock(lockKey);
        }
        //8.返回
        return shop;
    }



    public Shop queryWithPassThrough(Long id) {
        String key = CACHE_SHOP_KEY + id;

        //1. 从redis查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isNotBlank(shopJson)){
            //3. 存在，直接返回
            return JSONUtil.toBean(shopJson, Shop.class);
        }
        //判断命中是否为空值
        if (shopJson != null){
            return null;
        }
        //4.不存在，根据id查询数据库
        Shop shop = getById(id);
        //5.数据库不存在，返回错误
        if (shop == null){
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(key, "",CACHE_NULL_TTL, TimeUnit.MINUTES);
            // 返回错误
            return null;
        }
        //6.存在，写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);

        //7.返回
        return shop;
    }

    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private void unLock(String key){
        stringRedisTemplate.delete(key);
    }


    public void saveShop2Redis(Long id, Long expireSeconds){
        //1.查询店铺数据
        Shop shop = getById(id);
        try {
            Thread.sleep(200);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }
        //2.封装逻辑过期时间
        RedisData redisData = new RedisData();
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(CACHE_SHOP_TTL));
        //3.写入redis
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(redisData));
    }


    @Override
    @Transactional
    public Result update(Shop shop) {
        Long id = shop.getId();

        if (id == null){
            return Result.fail("店铺id不能为空");
        }
        //1.更新数据库
        updateById(shop);
        //2.删除缓存
        stringRedisTemplate.delete(CACHE_SHOP_KEY + id);

        return Result.ok();
    }
}
